Switch frog for the overhead conductors of electric traction systems



Dec. 24, 1940; BRQOM ETAL 2,225,766

SWITCH FROG FOR THE OVERHEAD CONDUCTORS OF ELECTRIC TRACTION SYSTEMSFiled Dec. 14, 1959 5 Sheets-Sheet 1 lA l IVTUF 724W w r ifi, M WME/MMDec. 24, 1940. c BROQM AL 2,225,766

SWITCH FROG FOR THE OVERHEAD CONDUCTORS OF ELECTRIC TRACTION SYSTEMSFiled Dec. 14, 1939 5 Sheets-Sheet 2 24, 1940- T. c. BROOM ET AL2,225,766

SWITCH FROG FOR THE OVERHEAD CONDUCTORS OF ELECTRIC TRACTION SYSTEMSFiled Dec. 14, 1939 5 Sheets-Sheet s Fig. 3.

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army/v57 1940- T. c. BROOM ETAL 2,225,766 7 SWITCH FROG FOR THE OVERHEADCONDUCTO RS OF ELECTRIC TRACTION SYSTEMS Filed Dec. 14, 1939 5Sheets-Sheet 4 Dec. 24, 1940. Q BROOM ETAL 2,225,766

SWITCH FROG FOR THE OVERHEAD CONDUCTORS 0F ELECTRIC TRACTION SYSTEMSFiled Dec 14, 1939 5 Sheets-Sheet 5 arrow 5y I Patented Dec. 24, 1940UNITED STATES PATENT OFFICE SWITCH FROG FOR THE OVERHEAD CON- DUCTORS FELECTRIC TRACTION SYS- TEMS Application December 14, 1939, Serial No.309,194 In Great Britain December 24, 1938 4 Claims.

This invention relates to automatically operable switch-frogs which areused in overhead electric traction systems, and is particularlyconcerned with switch-frogs which are adapted to be operated by currentcollectors moving along the associated conductors. Such a switch frogcomprises a switch-plate pivotally mounted so as to be movable about avertical axis, adapted to be set normally in a primary position topermit movement of a current collector in one path and to be movedautomatically into a secondary position by a collector enteringthe'switch-frog along another path. In both primary and secondarypositions the corresponding path is completed by a movable tongue formedintegral with, and consequently movable with, the switch-plate into orout of the desired position. A switch-frog of this nature may be a crossover, the entry side of which is approached by two paths which intersectand continue from the'exit side of the frog as separate paths. Inanother form the switchfrcg may be a trailing frog, the entry side ofwhich may be approached by a collector moving along either of two pathswhich converge to form a single path extending from the exit side of thefrog. With this latter form of switch-frog the switch-plate may beformed with two movable tongues, one adapted to complete a path in theprimary position, and the other adapted to complete the other path inthe secondary position, and each tongue being movable into aninoperative position as the other tongue is moved into an operativeposition. The path which is completed when a movable tongue is in theprimary position will be referred to as the primary path, and the otherpath, completed by a tongue in the secondary position, will be referredto as the secondary path.

According to this invention a switch-frog is provided with meansoperable by a current collector to move a switch-plate into thesecondary position as a collector enters the switch-frog along thesecondary path, and into the primary position as the collector leavesthe switch-frog. The switch-plate is normally set in the primaryposition, a movable tongue formed thereon thereby completing the primarypath, which may conveniently be the most frequently used path.Furthermore, the invention also provides means whereby the switch-plateis locked automatically in both primary and secondary positions, so thatit cannot be displaced by any lateral forces which may be exerted by thepassing collector.

The improved means comprises two cranks,

each rotatable about a vertical axis located at the side of the frog,one crank, referred to hereinafter as the entry crank, being locatedadjacent the secondary path on the entry side of the frog, and theother, hereinafter named the exit crank, being similarly located on theexit side of the frog. The cranks are so coupled together and to theswitch-plate that rotation of either crank effects simultaneous movementof the switch-plate and of the other crank. Each crank is adapted tooccupy an operable position in which it will be engaged by a collectormoving along the adjacent secondary path and to be moved thereby into anoperated position. The relative disposition of the interconnected cranksand switch-plate is such that when a tongue is in the primary positionthe entry crank is in the operable position, and the exit crank is inthe operated position. The entry crank is adapted to be turned into theoperated position by engagement with an entering collector, a movabletongue being thereby moved into the secondary position, and the exitcrank being simultaneously turned into the operable position. The exitcrank is adapted to be returned to the operated position by engagementwith the collector leaving the frog, thereby resetting the primary pathby returning a movable tongue into the primary position, and at the sametime turning the entry crank into the operable position whereby themechanism is again set to be operated by the next collector which entersalong the secondary path.

The relative disposition of the coupling between the cranks andswitch-plate is such that in both primary and secondary positions anyforce directed from' the switch-plate to the cranks acts in a directionpassing through the axis of rotation of one of the cranks, therebyensuring that the cranks cannot be rotated by the application of such aforce. Each crank is also acted upon by a biassing force to ensure thatthe mechanism moves completely into the secondary position upondisplacement by an entering collector, and completely into the primaryposition upon displacement by the collector on leaving, a fixed stopbeing associated with each crank to determine the extent of its movementinto the operable position.

Each crank may comprise one arm of a bellcrank lever mounted in abracket onthe side of the body of the frog. The other arm of thebellcrank may be coupled to the switch-plate by a connecting rod,pivotally connected with the bellcrank and switch-plate, and capable oftransmitting movements both under tension and compression. The relativedispositions of cranks and connecting rods may be such that in theprimary position one connecting rod extends in a direction passinthrough the centre of rotation of its associated crank and in thesecondary position the other connecting rod is similarly disposed withrelation to its associated crank. The biassing forces, whereby thecomplete movement of one crank into the secondary position and of theother crank into the primary position are ensured, may be provided by aspring associated with each crank in such a manner that the forceexerted by a spring, through its associated crank, on the connecting rodincreases as the crank approaches the position towards which it is urgedby the spring.

In order to minimise the wear of the projecting portion of each crankand of the collectors which engage it, that portion of the crank whichprojects into the secondary path may be constituted by the surface of afreely rotatable wheel mounted on the crank. The rim and central part ofthe wheel may be distinct members separated by a resilient constructioncapable of absorbing the shock of the impact between the rim and acurrent collector. The resilient means may consist of a rubber filling,or a spiral spring attached to both rim and central part, or any othersuitable device.

The invention is further described by way of example hereinafter withreference to the accompanying drawings which illustrate a cross-overadapted to be used at theiin-tersection of a primary and a secondarypath, and to provide for the passage of a current collector in eitherdirection along the primary path and in one direction only in thesecondary path. In the drawings Figure 1 is a view from above of part ofthe cross-over in the operable, or primary, position;

Figure 1A is a view from above of the other part of the arrangementshown in Figure 1;

Figure 2 is a view from below of partof the cross-over in the positionshown in Figure 1;

Figure 2A is a View from below of the other part of the arrangementshown in Figure 2;

Figure 3 is a view from above of part of the cross-over in the operated,or secondary, position;

Figure 3A is a View from above of the other part of the arrangementshown in Figure 3;

Figure 4 is a view from below of part of the cross-over in the positionshown in Figure 3;

Figure 4A is a view from below of the other part of the arrangementshown in Figure 4;

Figure 5 is a side view of part of the cross-over in the primaryposition; I I

Figure 5A is a side view of the other part of the arrangement shown inFigure 5;

Figure 6 is a diagrammatic illustration of part of' the cross-overshowing the relative positions of the movable parts in both primary andsecondary positions; and

FigurefiA is a diagrammatic illustration of the other part of thearrangement shown in Figure 6.

The cross-over consists of a body I provided on the-underside thereofwith four fixed tongues, each of which is adapted to be connected at itsouter end in any known manner with an overhead tra'ction conductor. Thefixed tongues are arranged in pairs, one pair 2, 2 being in alignmentwith the conductors which form the primary path P, and the other pair 3,3 being in alignment with the conductors which form the secondary pathS. A switch-plate in the form of a movable tongue 4 is pivotally mountedat its centre point on the underside of the body I. The movable tongueis capable of being turned about a vertical axis 5 at its centre point,which coincides with the intersection of the two paths, to completeeither the primary or the secondary path. In Figure 2 the movable tongue4 is shown in the primary position bridging the gap between the pair ofprimary fixed tongues 2, 2 to form the primary path. In Figure 4 thetongue is shown in the secondary position, bridging the gap between thepair of secondary fixed tongues 3, 3 to form the secondary path. Thecross-over is adapted, in the primary position, to permit the movementof a current collector 3| in either dimotion along the primary path asindicated by the double-ended arrow P, but in one direction only alongthe secondary path as indicated by the arrow S. The end of thecross-over which is approached by a current collector moving in thesecondary path is referred to as the entry side, the other end beingreferred to as the exit side. At the entry side of the cross-over andadjacent the fixed secondary tongue 3 a bracket 6 is bolted to a seatingI formed on the side of the body I. A vertical pivot pin I, freelyrotatable in the bracket 6, carries at its lower end a bifurcated arm 8and at its upper end an arm 9. The upper arm 9 is clamped to the pivotpin I and is set at an angle of about 60 to the lower arm 8, so that thetwo arms 8 and 9 function as a bellcrank. The end of the bifurcated arm8 carries a wheel 32 freely rotatable about a vertical axis andconsisting of a metallic rim II connected with the hub of the wheel by aresilient disc of rubber I2. On the upper end of the pivot of themovable tongue 4 is clamped a horizontal projection I6. A connecting rodI3 is pivotally joined at one end I5 to the projection I6 and at itsother end I4 to the upper arm 9 of the bellcrank. At the exit end of thecross-over there is a similar arrangement of bracket 22 bolted to aseating 23 formed on the side of the body I adjacent the other fixedsecondary tongue 3, carrying a bell-crank consisting of an upper arm 24and a lower arm 25 fixed to a common pivot 25 which is freely rotatableabout a vertical axis in the bracket 22. The lower arm 25 carries at itsouter end a freely rotatable pulley 33 having a metallic rim 21. Theconnecting rod 28 is pivotally attached at one end 29 to the upper arm24 and at the other end 30 to the projection I6.

At a short distance from its point of connection I-5 with the projectionIt the first mentioned connecting rod I3 carries a horizontallyprojecting arm I8. The other connecting rod 28 similarly carries aprojecting arm I9. Both of the arms I8 and I9 extend substantially atright angles with the associated connecting rods, in a direction awayfrom the intersection of the paths. The ends of these arms I8 and I9 areconnected by a helical spring I! maintained under tension. It will beappreciated from Figure 5 that the projection IS, the connecting rods I3and 28, and the upper arms 9 and 24 of the bell cranks lie substantiallyin the same horizontal plane of rotation in which the spring I1 is alsolocated.

When the cross-over is normally set in its primary position, in whichthe movable tongue completes the primary path (Figures 1 and 2), thebell-crank on the entry side is in such a position that the rim II ofthe associated wheel 32 projects into the path of movement of a currentcollector 3| entering along the secondary path S. In this position thelower arm 8 of the bell crank lies against a fixed stop 20 and theconnecting rod [3 extends, together with the upper arm 9 of the bellcrank, in line with the axis of rotation I of the bell crank. Theconnecting rod I3 is thus in a dead centre position with reference tothe bell-crank, which cannot, therefore, be rotated by a force exertedalong the connecting rod 13 from the movable tongue 4. The movabletongue 4 is thus effectively locked in the primary position in alignmentwith the fixed tongues 2, 2 to complete the primary path. The otherbell-crank, that is on the exit side, is in such a position that the rim2'! of the associated wheel 33 is held clear of the adjacent secondarypath S, the upper arm 24 of the bell-crank and the associated connectingrod 28 being out of alignment as shown. The relative arrangement of themovable parts in the primary position is indicated in full line in thediagrammatic Figure 6.

The other position of the movable tongue, that is, the secondaryposition, is shown in Figures 3 and 4, and in this position the bellcrank at the entry side is turned into such a position that theassociated wheel 32 is held clear of the secondary path S, the upper arm9 of the bellcrank and the connecting rod l3 being out of alignment. Onthe exit side of the crossing the bell-crank is in such a position thatthe rim 21 of the wheel 33 overlaps the secondary path S and the upperarm 24 of the bell-crank and the assooiated connecting rod 28 aretogether in line with the axis of rotation 26 of the bell-crank. Theconnecting rod 28 is thus in a dead centre position when the movabletongue 4 is in the secondary position, thereby locking the tongue inthis position. The relative arrangement of the movable parts in thesecondary position is indicated in dotted lines in the diagrammaticFigure 6.

The operation of the mechanism is as follows. The cross-over is in theprimary position as a current collector 3| approaches the entry sidealong the secondary path S (Figures 1 and 2). The collector strikes thewheel rim H and partially rotates the associated bell-crank in thedirection of the arrow A. During the initial part of this rotation theangular movement of the connecting rod I3 is great compared with aslight movement of the movable tongue 4. In consequence, the movement ofthe connecting rod about the point of connection I5 with the projectionI 6 causes the spring I! to be stretched. As the rotation of thebell-crank proceeds the connecting rod I3 is subjected to a longitudinalmovement and the extension I6 is rotated so that the movable tongue ismoved towards the secondary position as indicated in Figures 3 and 4 andthe other connecting rod 28 approaches the dead centre position withreference to the pivot 6 of the bell-crank on the exit side. During thefinal stage of the movement the spring l1, being under tension, tends tocollapse and pulls the connecting rod 28 and the upper arm 24 of thebellcrank lever on the exit side into the dead centre position, in whichthe lower arm 25 of the bellcrank is arrested by a fixed stop 2!. Therim 21 of the wheel 33 on the exit side now overlaps the secondary pathS.

The current collector 3i traverses the movable tongue now in thesecondary position (Figures 3 and 4) and eventually strikes the wheelrim 21, causing the associated bell-crank to be rotated in the directionof the arrow B. The various parts of the mechanism now move in a reversemanner to that above described, the connecting rod I3 on the entry sidebeing drawn by the spring I! into the .dead centre position, and themovable tongue returned to the primary position. The movable tongue hasthus been automatically moved from the primary position by the entry ofa current collector along the secondary path S and automaticallyreturned to the primary position as the current collector leaves thecross-over. It is locked in both primary and secondary positions, and isonly displaced from the primary position during the short time in whichthe current collector, moving along the secondary path, traverses thecross-over between one wheel 32 on the entry side and the other wheel 33on the exit side.

It will be appreciated in what manner the invention can be applied to atrailing frog. In a frog of this form there will be provided only onefixed tongue, on what has been called the exit side, to combine bothprimary and secondary 0 paths in a common path. A movable tongue, oraswitch-plate on which one or two tongues may be formed, will be pivotedabout a suitable point so that in the primary position the primary pathwill be completed between the primary fixed on the exit side, the tonguewill be locked in I position, and a collector will be enabled to movefreely in either direction along the primary path. In this position alsothe Wheel (such as the wheel 32 above described) on the entry side Willoverlap the secondary path, so that on the approach of a currentcollector along that path, the mecha- In the other position nism will beimmediately operated to move the apparatus into the secondary position,and as the collector leaves along the common path the apparatus will bereset.

The arrangement of the cross-over which has been described may bere-adjusted in several Ways. For instance, it may be arranged in such amanner that the secondary position is obtained by the passage of acurrent collector in a direction opposite to that already indicated.This is readily eifected by altering the positions of the fixed stops 2tand 2|, and by adjusting on their axes of rotation the various movablemembers in such a way in relation to one another that in the primaryposition the wheel 33 overlaps the secondary path and the other wheel 32is held clear of that path. The connection of the projection IS with themovable tongue will be required to be slackened and reset with thelatter in its desired setting and the former on the 0pposite side of thepoint of intersection. Furthermore, the body I of the cross-over isprovided with additional sea-tings 34 and 35 on which the brackets 6 and22 may be mounted for the purpose of reversing the primary and secondarypath, so that the above described secondary position of the movabletongue now becomes the normal position. These changes can similarly bemade in connection with the apparatus as applied to a trailing frog.

What We claim as our invention is:

1. In a switch-frog for an overhead traction conductor system, a movableswitch-plate having a primary and a secondary position, means op-'erable by a current collector moving in a secondary path to move theswitch-plate from the primary to the secondary position as the collectorenters the frog and to return the switch-plate to the primary positionas the collector leaves the frog, the said means comprising an entrycrank projecting into the secondary path when the switch-plate is in theprimary position, an exit crank projecting into the secondary path whenthe switch-plate is in the secondary position, coupling means connectingthe cranks and switchplate whereby movement of either crank producessimultaneous rotation of the other crank and of the switch-plate, and,in the primary and in the secondary position, force applied through theswitch-plate to one of the cranks acts in a direction passing throughthe axis of rotation of that crank.

2. In a switch-frog for an overhead traction conductor system, a movableswitch-plate having a primary and a secondary position, means operableby a current collector moving in a secondary path to move theswitch-plate from the primary position to the; secondary position as thecollector enters the frog, and to return the switch-plate to the primaryposition as the collector leaves the frog, the said means comprising twobell-cranks, an arm of one bell-crank projecting into the secondarypathwhen the switch-plate is in the primary position, an arm of theother bell-crank projecting into the secondary path when theswitch-plate is in the secondary position, connecting rods coupling theother arms of the bell-cranks to the switch-plate, one connecting rodbeing on dead-centre in the primary position and the other connectingrod being on dead-centre in the secondary position, each with referenceto the centre of rotation of its associated crank.

3. In a switch frog for an overhead traction conductor system, a movableswitch-plate having a primary and a secondary position, means operableby a current collector moving in a secondary path to move theswitch-plate from the primary to the secondary position as the 001-lector enters the frog, and to return the switchplate to the primaryposition as the collector leaves the frog, the said means comprising anentry crank projecting into the secondary path when the switch-plate isin the primary position and an exit crank projecting into the secondarypath when the switch-plate is in the secondary position, coupling meansconnecting the cranks and switch-plate whereby movement of either crankproduces simultaneous rotation of the other crank and of theswitch-plate, and, in the primary and in the secondary position, forceapplied through the switch-plate to one of the cranks acts in adirection passing through the aXis of rotation of that crank, biassingmeans acting upon the said cranks and ensuring that the mechanism movescompletely into the secondary and primary positions, and a fixed stopassociated with each crank to determine the extent of the movement ofthat crank into the secondary path.

4. In a switch-frog for an overhead traction conductor system, a movableswitch-plate having a primary and a secondary position, means operableby a current collector moving in a secondary path to movethe-switch-plate from the primary position to the second position as thecollector enters the frog, and to return the switchplate to the primaryposition as the collector leaves the frog, the said means comprising twobell-cranks, an arm of one bell-crank projecting into the secondary pathwhen the switch-plate is in the primary position, an arm of the otherbell-crank projecting into the secondary path when the switch-plate isin the secondary position and the other arm of each bell-crank beingcoupled to the switch-plate by a connecting rod, and spring means actingon the connecting rods whereby is ensured the complete movement of eachconnecting rod with its crank arm into a dead centre position.

TALBOT COTTOM BROOM. HOWARD JENKINS POWELL.

